W3C home > Mailing lists > Public > www-rdf-interest@w3.org > April 2001

RE: URIs / URLs

From: Charles McCathieNevile <charles@w3.org>
Date: Thu, 12 Apr 2001 08:41:08 -0400 (EDT)
To: Lee Jonas <lee.jonas@cakehouse.co.uk>
cc: "'Aaron Swartz'" <aswartz@swartzfam.com>, RDF Interest <www-rdf-interest@w3.org>, RDF Logic <www-rdf-logic@w3.org>
Message-ID: <Pine.LNX.4.30.0104120832270.18863-100000@tux.w3.org>
On Thu, 12 Apr 2001, Lee Jonas wrote:
[snip]
  If Pierre-Antoine leaves example.edu and is replaced by Jean-Claude Champin,
  who puts his home page in the same place at 'http://example.edu/~champin'
  then not only has the representation (html doc) changed, but the same
  location ('http://example.edu/~champin') now identifies Jean-Claude (or
  Jean-Claude's conceptual home page, etc).

  I.e. the same URI identifier has changed from identifying Pierre-Antoine to
  identifying Jean-Claude (or repective home pages, etc).

  Taking 'http://example.edu/~champin/' to identify "the person named Champin
  currently enrolled at Example University" as you said above implies that
  URLs do not identify these resources through representations, but identify
  mappings-to-resources through representations instead.  This would have very
  serious ramifications for RDF.

  Regardless of the interpretation of Resource, doesn't it strike you as a
  major blow to writing metadata statements about URLs that remain correct
  over time?  Consider making assertions about Pierre-Antoine only to find 3
  months later that those assertions are are actually making (probably false)
  statements about Jean-Claude instead.

No, it strikes me as a major blow to the Web if someone makes an assertion
that is about Pierre-Antoine, but expresses it as being about "the person
enrolled whose surname is Champin", and then expects the rest of the web to
understand the implicit logic leap that their statement is about the current
referrent at the time of the statement and not the actual thing identified
(i.e. the confusion between an idea and an instance).

W3C says that it won't change a URI that begins http://www.w3.org/xxxx/ where
xxxx is a year identifed in the "Common Era" (what used to be called years
anno domini). So if W3C uses one such URI to identify me, and another to
identify the staff contact for the authoring tool guidelines working group,
and another to identify the team member who eats the most vegemite, someone
who wants to make an assertion about me should use the correct identifier.
Likewise to talk say something about whoever eats the most vegemite (for
example, that nobody is likely to steal their toast), it makes sense to use
the correct URI, and not just assume that that will be me for ever.

[snip]
  I believe the "exact meaning" of URLs should be constant, simple and well
  known.  Judging from discussions on RDF-IG so far, 1 out of 3 isn't so great
  ;-)

Right. And the best way to do that is for the creator of the URI to say what
the URI means, not for a third party to guess and then assume that their
guess is correct. (Until we get the telepathic web).

cheers

Charles
Received on Thursday, 12 April 2001 08:41:12 GMT

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